1. Field of the Invention
This invention relates to the preparation of multifunctional additives from cashew nut shell liquid.
2. Description of the Related Art
This invention relates to a process for the preparation of amino di(alkylaryl)phosphorodithioates, from naturally occurring, biodegradable, vegetable based cashew nut shell liquid, for use in a lubricant, so as to impart suitable properties of friction reducing, antioxidant, antiwear and extreme pressure additives.
Cashewnut shell liquid (CNSL) occurs as a reddish brown viscous liquid in the soft honeycomb structure of the shell of cashewnut, a plantation product obtained from the cashew tree, Anacardium Occidentale L. Native to Brazil, the tree grows in the coastal areas of Asia & Africa. Cashewnut attached to cashew apple is grey colored, kidney shaped and 2.5-4 cm long. The shell is about 0.3 cm thick, having a soft leathery outer skin and a thin hard inner skin. Between these skins is the honeycomb structure containing the phenolic material popularly called CNSL. Inside the shell is the kernel wrapped in a thin brown skin, known as the testa.
The nut thus consists of the kernel (20-25%), the shell liquid (20-25%) and the testa (2%), the rest being the shell. CNSL, extracted with low boiling petroleum ether, contains about 90% anacardic acid and about 10% cardol. CNSL, on distillation, gives the pale yellow phenolic derivatives, which are a mixture of biodegradable unsaturated m-alkylphenols, including cardanol. Catalytic hydrogenation of these phenols gives a white waxy material, predominantly rich in tetrahydroanacardol.
CNSL and its derivatives have been known for producing high temperature phenolic resins and friction elements, as exemplified in U.S. Pat. Nos. 4,395,498 and 5,218,038. Friction lining production from CNSL is also reported in U.S. Pat. No. 5,433,774. Likewise, it is also known to form different types of friction materials, mainly for use in brake lining system of automobiles and coating resins from CNSL.
Friction is also a problem any time two surfaces are in sliding or rubbing contact. It is of special significance in an internal combustion engine and related power train components, because loss of a substantial amount of the theoretical mileage from a gallon of fuel is traceable directly to friction.
It is also known that sliding or rubbing metal or other solid surfaces are subject to wear under conditions of extreme pressure. Wear is particularly acute in modern engines in which high temperatures and contact pressures are prevalent. Under such conditions, severe erosion of metal surfaces can take place even with present generation lubricants unless a load carrying or antiwear additive is present therein. These load carrying, friction reducing, antiwear and antioxidant additives are generally organic compounds, having polar groups, which are capable of forming a film at the mating metal surfaces.
Considerable work has been reported with lubricating oils, mineral and synthetic, to enhance their antioxidant, antiwear and friction reducing properties, by modifying them with suitable additives. The use of lubricant additives containing phosphorus and sulfur has been well documented and widely implemented commercially. These include acid phosphates, thiophosphates, phosphites, phosphate ester, metal dithiophosphates, metal dithiocarbamates, xanthates, phosphonates and the like. Amine compositions have also found wide use as friction reducing additives as exemplified by U.S. Pat. No. 4,328,113 which relates to alkyl amines and diamines and borated adducts of alkylamine and diamines. U.S. Pat. 4,478,732 describes imidazoline salts of acid phosphates, while U.S. Pat. 4,505,830 is drawn to C10-C20 alkyl substituted imidazoline salts of boric acid or phosphoric acid as useful in metal working lubricants. U.S. Pat. 4,618,437 describes boronated internal imidazoline acid phosphates as effective friction reducers.
The present invention relates to lubricant compositions and more particularly, to lubricant compositions comprising oils of lubricating viscosity or greases thereof containing a minor friction reducing, antiwear and antioxidant additive of hydrocarbyl amine salt of di(alkylaryl)phosphorodithioic acid derived from cashew nut shell liquid.
An object of this invention is to propose a process for the preparation of various amine salts of di(alkylaryl)phosphorodithioic acids, derived from cashew nut shell liquid, which when blended into lubricants, provide effective multifunctional friction reducing, antioxidant, antiwear and extreme pressure activities.